WO2014111111A1

WO2014111111A1 - Steering wheel with improved interface to a finger navigation module

Info

Publication number: WO2014111111A1
Application number: PCT/EP2013/003780
Authority: WO
Inventors: Kwok Chiu CHEUNG; Volker Entenmann; Andreas Kail; Jing MU; Jörg REISINGER; Manuel Stotzem
Original assignee: Daimler Ag
Priority date: 2013-01-19
Filing date: 2013-12-14
Publication date: 2014-07-24
Also published as: EP2946271B1; CN104919401A; DE102013000944A1; EP2946271A1; US20150355737A1

Abstract

The intention is to reduce the construction space requirement for a steering wheel with a steering wheel electronics unit (2) connected via a communications device to an optical finger navigation module (1, 1'). The communications device comprises a data bus with only three lines (11, 12, 13 or 11', 12', 13'). Two of the three lines are designed for data transmission and one for clock pulse transmission. Due to the limitation to the three lines, the construction space is reduced and the data bus ensures the necessary immunity to interference.

Description

Steering wheel with improved interface to a finger navigation module

The present invention relates to a steering wheel for a motor vehicle with an optical finger navigation module, a steering wheel electronics and a communication device for data transmission between the optical finger navigation module and the

Steering wheel electronics.

In the switch block of a vehicle steering wheel, an optical finger navigation module (OFN) can be integrated as a sensor for the detection of finger movements. The

Sensor data must be transmitted via a data bus connection from the OFN to the steering wheel electronics (LRE); see. Fig. 1) are transmitted. It is the for the plug and

Cable connections available space in the steering wheel severely limited. In addition, the communication between the OFN and the steering wheel electronics should be robust against external interference and be synchronized with the data transfer from the steering wheel electronics to a jacket tube switch module in the steering column.

Frequently an OFN 1 is also used in the so-called "consumer electronics" (see Fig. 2), where the OFN 1 is connected directly to a printed circuit board 2 on which a microcontroller 3 is located, which evaluates the OFN data.

In consumer electronics, OFN 1 and microcontroller 3 generally communicate with one another via an I 2 C interface (Inter-Intergrated Circuit). This serial

Interface is designed for communication between controllers on a board and requires only two signal lines 4 and 5 (Serial Clock SCLK and Signal Data SDA). If the OFN detects a finger movement on its surface, it initiates one

Communication with the microcontroller 3 by making an interrupt to the

Microcontroller 3 sends. For this purpose, an interrupt line 7 (MOTION_N) between the OFN 1 and the microcontroller 3 is required. Overall, three lines are necessary for the operation. However, the immunity to interference of the I2C interface for motor vehicle applications is not sufficient for the data transmission between the OFN 1 and the LRE via long signal lines which is necessary in the steering wheel. Rugged enough for use in a motor vehicle steering wheel would be a known "SPI" interface (Serial Peripheral Interface). A connection of an OFN via an SPI interface to a microcontroller 3 is shown schematically in FIG. As in the example of FIG. 2, the circuit board 2 of the steering wheel electronics LRE is equipped with the microcontroller 3. The electronics 6 of the OFN 1 is arranged on a printed circuit board 8 of a multi-function switch (MFS). The microcontroller 3 and the electronics 6 of the OFN 1 each have an SPI interface 9, 10. This SPI interface requires four data lines by default. Three data lines 11, 12 and 13 are needed for the actual data transfer, namely SCLK (Serial Clock), MOSI (Master Out Slave In), MISO (Master In Slave Out). Via the fourth line 14 (SS, Slave Select), the master (in this case the microcontroller 3) selects the slave (in this case OFN 1) with which he wishes to communicate. In principle, multiple slaves can thus communicate with one master, whereby the slaves can share the three data lines, but each need their own slave select line. From the four signal lines of the SPI interface 9, 10, however, results in an increased space requirement in the steering wheel for the plug 15, 16 on the two circuit boards 2, 8 and the corresponding cable set. In addition there is the space requirement for a fifth line 17, which is necessary for the interrupt procedure similar to the example of Fig. 2.

In consumer electronics, the data transmission between the microcontroller 3 as a master and the OFN 1 as a slave is initiated by the OFN 1. This is your own

Signal line 17 used for the so-called motion interrupt. The OFN 1 detects a change in the state of touch or movement of the finger on his

Surface, it sends a motion interrupt to the master 3. This then starts the query OFN data via the serial interface 9, 10th

This communication concept has the advantage for consumer electronics that event-dependent communication between master and slave is only possible when a finger movement takes place. This results in a minimum energy requirement, which is an important aspect for mobile devices. For the application in the steering wheel, this aspect is two-tiered. A disadvantage for the application in the steering wheel is that an additional signal line is needed for the motion interrupt, which further aggravates the installation space problem. On the other hand, this event-based communication is difficult to follow Synchronize the ongoing cyclic data transmission between the steering wheel electronics and jacket tube switch module.

The object of the present invention is thus to provide a steering wheel which allows interference-free operation of an OFN with a small space requirement.

According to the invention this object is achieved by a steering wheel according to claim 1.

Advantageous developments of the invention will become apparent from the dependent

Claims.

In addition, a motor vehicle is provided with a corresponding steering wheel.

An inventive steering wheel for a motor vehicle is thus equipped with an optical finger navigation module, a steering wheel electronics and a communication device for data transmission between the optical finger navigation module and the steering wheel electronics. In this case, the communication device comprises a serial data bus with only three lines, wherein two of the three lines for

Data transmission and one are designed for clock transmission.

In an advantageous manner, therefore, a data bus with only three lines is provided between the optical finger navigation module and the steering wheel electronics.

Compared to four or five lines, a significant saving in space has thus been achieved. Characterized in that two lines are provided for the data transmission, in a development of the steering wheel according to the invention also a line for communication from the steering wheel electronics to the OFN and the other data line for the communication can be used in the reverse direction, whereby the

Noise immunity is further improved.

Preferably, the steering wheel electronics is configured to poll the OFN module cyclically via the communication device. This cyclic polling makes it possible to dispense with a separate interrupt line.

In particular, the data bus may be an SPI data bus. This is characterized by sufficient immunity to interference. The OFN module may be further configured to detect a finger movement on the surface of the OFN module as at least one difference value describing a distance traveled by a finger in a communication cycle. By the difference value can be reliably detected, whether a finger on the

Surface of the OFN module has moved.

Specifically, the OFN module may calculate a sum value from a plurality of difference values and transmit the sum value over the

Communication device to be formed to the steering wheel electronics. Furthermore, the steering wheel electronics can be designed to calculate a difference value as an indicator for a finger movement from a transmitted summation value and a stored further summation value. If, therefore, sum values are transmitted by the OFN module, the sum values can also be concluded of a movement on the receiving side by processing, in particular difference value formation, even if a data value is not transmitted due to an error.

In another embodiment, the steering wheel electronics are adapted to control a temperature compensation of the OFN module based on internal data stored or provided in the steering wheel electronics. This has the advantage over the usual temperature compensation, in which only internal data of the OFN module are used, that also data which are obtained outside the steering wheel electronics or outside of the OFN module, such as ambient temperature,

Interior temperature, etc., can be used for temperature compensation.

In addition, the steering wheel electronics can be equipped with a microprocessor which has at least two SPI interfaces, whereby the OFN module is connected via one of the SPI interfaces and another OFN module is connected via another one of the SPI interfaces. This makes it possible to connect the OFN modules of two switch blocks of a steering wheel in accordance with the invention advantageously with a central steering wheel electronics.

The steering wheel may also be in communication with a jacket tube switch module of a steering column, wherein a communication between the OFN module and the steering wheel electronics with a communication between the Steering wheel electronics and the jacket tube switch module is synchronized. These

Synchronization has the advantage of a time-optimized transmission.

Specifically, it is advantageous if a motor vehicle is equipped with the steering wheel according to the invention.

The present invention will be further explained with reference to the accompanying drawings, in which:

Fig. 1 is a schematic sketch of a steering wheel with optical

Finger Navigation modules;

2 shows an OFN module, which according to the prior art has an I 2 C-

Interface is connected;

3 shows an OFN module, which according to the prior art has a 4-wire SPI

Interface is connected and

Fig. 4 shows an OFN module connected according to the invention with a 3-wire SPI interface.

The embodiments described in more detail below are preferred

Embodiments of the present invention.

In Fig. 1, a steering wheel 18 is shown schematically. On the steering wheel are here in ergonomically suitable positions two switch blocks 19 and 20, which also as

Multifunction switch (MFS) can be designated. In other

Embodiments is only one such switch block or are more than two switch blocks or multi-function switch provided.

In the example of Fig. 1, each switch block 19, 20 has an optical

Finger navigation module (OFN). In addition, the switch blocks 19 and 20 each have other mechanical controls 21. To transmit the data from the left switch block 19 to a steering wheel electronics 22 (LRE) is a cable 23, which is equipped at its ends with plugs 24. Analogously, the communication takes place from the right switch block 20 to the steering wheel electronics 22 via a cable 25. The signal output from the steering wheel electronics 22 to, for example, a

Jacket tube switch module (not shown in Fig. 1) via another cable 26th

As already mentioned, each OFN 1 serves as a sensor for the detection of finger movements. The cables 23 and 25 serve to realize a

Data bus connection or communication device between the OFN modules 1 and the steering wheel electronics 22nd

The communication connection between the OFN modules (short: OFN) and the steering wheel electronics 22 is shown schematically in FIG. Also in this example, the steering wheel with two OFN 1 and 1 'is formed. However, the number may vary depending on the embodiment as mentioned above.

As in the example of Fig. 3, a plug 6 on the printed circuit board 8 of

Multifunction switch arranged. The OFN 1 is connected to the printed circuit board 8 via the plug 6. The OFN 1 has a 3-wire SPI interface 27, via which it communicates with the microcontroller 3, which is located on the printed circuit board 2 of the steering wheel electronics. The first cable 23 with the plugs 24 is designed in accordance with three wires and connects the circuit board 8 with the circuit board. 2

The microcontroller 3 on the circuit board 2 of the steering wheel electronics has a first 3-wire SPI interface 28. The three signal lines 11 to 13 correspond to the first three signal lines of the 4-wire SPI interface of the example of FIG.

Accordingly, the signal line 11 is assigned to the "Serial Clock" SCLK, the data line 12 to the "Master Out Slave In" MOSI and the data line 13 to the "Master In Slave Out" MISO.

Analogously, the right OFN 1 ', the plug 6' is arranged on the circuit board 8 'of the right multifunction switch, data technically connected to the microcontroller 3 of the steering wheel electronics on the circuit board 2. For this purpose, the OFN 1 'also has a 3-wire SPI interface 27', which is connected to a corresponding 3-wire SPI interface 28 'of the microcontroller 3 via the cable 25 with the plugs 24. The three signal lines 11 'to 13' (also called data lines for the sake of simplicity) carry the signals or data SCLK, MOSI and MISO analogously. The microcontroller 3 is connected via a data bus 29 with further electronics, in particular a jacket tube switch module. The data bus 29 may be a LIN or CAN bus.

In the case of the communication connection or device according to the invention, therefore, a 3-wire SPI interface is selected for the OFN 1, 1 'in which the slave select and the motion interrupt lines are dispensed with. This results in a corresponding space advantage over the realization of Fig. 3 at

consistent immunity to interference.

Due to the topology in the steering wheel, the left and right OFN 1, 1 'anyway via their own cable 23, 25 are connected to the steering wheel electronics. That is, each OFN has its own SPI data lines 11 to 13 and 11 'to 13' as described above. Is now used in the steering wheel electronics, the microcontroller 3 with the two SPI interfaces to which the respective OFN is connected, can be dispensed with the slave select lines. Namely, there is only one slave (OFN) per SPI interface 28, 28 ', which is always active and communicates with the master (LRE or microcontroller 3).

In addition, the communication between the steering wheel electronics LRE and OFN is controlled exclusively by the LRE as the master. The LRE continuously polls each OFN at short intervals, that is, cyclically, so that changes in the finger state are quickly detected. The resulting from this query strategy, compared to an event-driven communication slightly increased energy demand is for the

Application in the steering wheel acceptable. The advantages are that the motion interrupt line is no longer needed and the SPI communication can be synchronized with the further data transmission via LIN or CAN bus to the casing tube switch module.

In addition to the hardware-side adaptation of the SPI interface, additional protocol-based optimizations can be made. This will be explained in more detail below.

The OFN 1 or 1 'typically detects a finger movement in the form of

Difference values Δχ and Ay that determine the movement of the finger in each

Coordinate direction (x and y axis) since the last data request via the serial Describe interface. In consumer electronics, these difference values are transmitted directly. If a message is lost due to external disturbances, there is no way to reconstruct its content from the previous and following message.

For this reason, the OFN 1 or V in the steering wheel does not transmit the difference values Δχ and Δ here, but rather the cumulative values x and y calculated continuously therefrom. Accordingly, the sum value x is calculated as the sum of all previous ones

Difference values Δχ and the sum value y as the sum of all previous ones

Difference values Ay. In the LRE, the difference values are then formed again by subtracting the last from the current summation values. If a message should be lost, the difference can also be calculated from the values of the following and the

previous messages are formed. So the loss of the message can be compensated.

In order to be able to detect the finger movement correctly under all temperature conditions, the OFN 1 or 1 'must from time to time carry out a temperature compensation of its sensor technology. In consumer electronics, the OFN determines the time for it itself. Typically, the temperature compensation is automatically carried out in defined

Intervals. When used in the steering wheel, however, the LRE controls the temperature compensation in the OFN via the SPI interface. Due to the data connection with the vehicle (data bus 29), there are many contextual information in the LRE, by means of which it can be decided whether and at which time intervals

Temperature compensation is necessary. Relevant information is z. B. the

Ambient temperature, the interior temperature and the operating state of

Heated steering wheel.

The advantages of the 3-wire SPI interface between OFN and LRE are the minimal space requirement for the connectors and the cable set as well as the robust data transmission against external interference. With a total of three signal lines, no more cables are needed than in consumer electronics. At the same time, the OFN and the LRE can be spatially separated.

Claims

claims

1. steering wheel (18) for a motor vehicle with

an optical finger navigation module (1, 1 '),

- A steering wheel electronics (22) and

a communication device for data transmission between the

optical finger navigation module and the steering wheel electronics,

characterized in that

- The communication device comprises a data bus (11, 12, 13, 11 ', 12', 13 ') with two lines for data transmission and a line for clock transmission.

2. Steering wheel according to claim 1,

characterized in that

the steering wheel electronics (22) is adapted to the optical

Fingernavigationsmodul (1, 1 ') via the communication device cyclically query.

3. Steering wheel according to claim 1 or 2,

characterized in that

the data bus (1, 12, 13; 11 ', 12', 13 ') is an SPI data bus.

4. Steering wheel according to one of the preceding claims,

characterized in that

the optical finger navigation module (1, 1 ') is designed to have a

Finger movement on the surface of the optical finger navigation module to detect as at least one difference value that describes a distance covered by a finger in a communication cycle track.

5. Steering wheel according to claim 4, characterized in that

the optical finger navigation module (1, 1 ') is designed to calculate a sum value from a plurality of difference values and to transmit the sum value via the communication device to the steering wheel electronics (22).

6. Steering wheel according to claim 5,

characterized in that

the steering wheel electronics (22) is adapted to be transmitted from the

Sum value and a stored further sum value to calculate a difference value as an indicator for a finger movement.

7. Steering wheel according to one of the preceding claims,

characterized in that

the steering wheel electronics (22) are adapted to a temperature compensation of the optical finger navigation module (1, 1 ') based on internal, in the

Steering wheel electronics stored or provided data control.

8. Steering wheel according to one of the preceding claims,

characterized in that

the steering wheel electronics (22) are equipped with a microprocessor (3) which has at least two SPI interfaces (28, 28 '), wherein the optical finger navigation module via one of the SPI interfaces and a further optical one via another of the SPI interfaces Finger navigation module is connected.

9. Steering wheel according to one of the preceding claims,

characterized in that

it with a jacket tube switch module a longitudinal column in

Communication link, and communication between the optical finger navigation module (1, 1 ') and the steering wheel electronics (22) with a communication between the steering wheel electronics (22) and the

Casing tube switch module is synchronized.

10. Motor vehicle with a steering wheel according to one of the preceding claims.